The Design of Impulse Buying

Impulse buying occurs when people make sudden, unplanned purchases. In consumer psychology, this behaviour is often linked to impulsive personality traits. When visiting a store, it is easy to see how various techniques are used to influence what people buy. This thesis examines how visual cues, like colours and visual clutter, affect impulse buying and how these cues interact with a person's impulsiveness.

University 

HMKW Berlin, Master's thesis

Duration · 4 months

April 2023

Examiner

Prof. Dr. Jan-Henning Raff,
Department of Design.
Prof. Dr. Volker Thoma,
Department of Psychology.

   The Gruen Effect in Online Retail, Explained  ·  Reading time: 95 seconds  

Understanding Impulse Buying

The Argument

Consumers describe external “forces” that influence them to buy impulsively (Rook, 1987).

A Snickers bar with googly eyes

“I was standing in the grocery store checkout line, and the candy bar was staring there at me.”

Interviewee in Rook's 1987 study.

Animation of a woman reading a book on psychology

Whereas psychologists focus on impulsive personality traits as the main explanation (Mandolfo et al., 2021).

Cartoon by Gary Larson set in front of a candy store

“The Far Side” cartoon by Gary Larson. Chronicle Features, San Francisco, CA. (1987)

Retail designer Victor Gruen transformed passersby into impulsive consumers by using light and space to dramatically stage products in storefronts (Hardwick, 2015).

Portrait of the retail architect Victor Gruen

“A good storefront tries to make his step as easy as possible for him and tries not to let him even notice that he takes such an important step.“

Victor Gruen (1941)

Hypothesis Building

Animation of excited shoppers in a supermarket

Overstimulation has been found to weaken behavioural regulation (Muraven et al., 1998).

The Gruen Effect describes a store that is so overwhelming that consumers are persuaded into consuming “mindlessly” (Hardwick, 2015).

Screenshot from the Zalando app with high visual clutter

Screenshot from the Zalando app with high visual clutter.

Visual clutter increases extraneous cognitive load (NN/g, 2013), and might also lead to overstimulation.

Hypothesis: High visual clutter will cause consumers to buy impulsively.

Creating Impulse Buying

Prototyping

Low visual clutter prototype screens

1. Low Visual Clutter Prototype

Low information load due to Gestalt laws of grouping and whole forms.

2. High Visual Clutter Prototype

High information load due to increased use of badges, unfinished forms, text cuts, inconsistency in colour coding, increased use of text and typographical scales, deconstructed hierarchy, and enforced algebra.

Animation of the high visual clutter prototype
The low and the high visual clutter prototype side by side

Comparison

A timed test showed that the high visual clutter prototype (on the right) significantly increased comprehension time by an additional 14 seconds on average.

Testing Impulse Buying

Experiment

Animation of the experiment method

106 participants: 45% women / 55% men / 0% diverse / Average age: 43 years. The general impulsiveness of the participants was assessed using the BIS-Brief Scale (Patton et al., 1995; Stanford et al., 2009).

Method

Participants were shown either a prototype with high or low visual clutter and asked to make a buying decision. Additionally, they were measured on impulsive personality traits.

Animation of the experiment results

A one-way ANOVA was conducted to examine the difference in participants' impulsive buying choices (dependent variable) between the two treatments (independent variable). The result was close to, but not below, the threshold for statistical significance, F(1, 44) = 3.9, p = .06 (alpha = .05). Male participants chose non-impulsive buying options across all conditions.

Result

The hypothesis was not supported: high visual clutter did not significantly increase impulsive buying choices. The clearest signal was among women, who chose more impulsive options with the high visual clutter prototype, but the difference was not statistically significant. Highly impulsive women did not choose more impulsive options than low-impulsive women, which hints that the shopping situation may matter more than personality. This remains a tentative pattern for future research, not a finding.